Catch all errors when recomputing values in a field-list and show a helpful dialog

[lognaturel]

This form has a select minimal with a value that gets used in a calculate for another select that was previously filtered to have no choices. It causes this crash. Because the second select's choices have never been rendered, choices are not attached to the selection.

Somewhat related, this crash can be reproduced by having a calculate on a select that produces a value not related to the choices. e.g. I put "foobar" in the calculate for a select that did not include "foobar" in its choices.

Also related to #4170.

People think they can use calculates as dynamic defaults. That will not work and they should not do that. In a way, it's not so bad that it crashes so catastrophically because at least they're not getting bad values which they would if the calculate succeeded. This can be fixed by adding a trigger. For example, in the sample form at top, add ${select} in the trigger column. That is how dynamic defaults are supposed to be expressed.

Could we perhaps catch all of these and show a better error message suggesting there might be a misuse of calculates?

[grzesiek2010]

It would be great to catch the exception and throw FormDesignException but it's not easy to identify that this is it...
Generally updating field-lit groups is a source of many possible issues so we could maybe just wrap everything in try-catch and display a dialog that something went wrong and it might be a form design issue.

[lognaturel]

wrap everything in try-catch and display a dialog that something went wrong and it might be a form design issue.

That sounds good to me. I've also filed a pyxform issue at XLSForm/pyxform#546 The Collect message could be something like Failure trying to update values. This is generally because of incorrect usage of calculations in the form design. + \n\nR.id.report_to_project_lead

Then the form should probably just close? It seems there's nothing of value that can be done with a form that has this kind of issue.

[lognaturel]

The two first cases with calculates and selects turn out to be the same as opening a record for edit. That is, there has to be an attempt to bind the selected answer(s) to the available choices or we can’t open a record for edit.